The portions of aural receiving devices of the prior art which fit in the wearer's ear are generally formed in one of several well known configurations. They may be pre-molded from either a moldable elastomeric material such as rubber or a synthetic polymer. Their purpose is primarily to retain the sound transmitting conduit in the ear and secondarily to screen out extraneous sound or noise. Among the devices formed in accordance with the prior art practice there are the well known simple, pre-molded channelled ear pieces commonly seen on stethoscopes and stenographic transcribers. No attempt is usually made to fit these to the individual and sound transfer into the receiver is usually less than satisfactory because of sound leaks around the outside surface of the pieces. They are normally uncomfortable if worn for long periods of time. Somewhat more sophisticated pre-formed devices are available from suppliers of hearing aids to handicapped individuals, and the like, and better results in terms of pure sound transmission are obtained because usually measurements are made of the ear before selecting the proper size of hearing receiver.
So far, the best permanent communications receiving devices for fitting all sizes and types of ears are made by custom-molding them to conform to the subject. This is commonly done with hearing aid receivers, for example. Another such custom-molded device is a valved, channelled hearing protector described in Wesemann, U.S. Pat. No. 3,603,309, for people like hunters who need noise protection when firing their guns, but wish also to be able to converse without the need to remove the protector, and do this by opening an internal ball valve on the channel. Such custom-molded pieces provide a positive fit and are more comfortable to the subject. It is the practice to prepare an impression of the subject's ear, make a mold and then cast a device in the mold which, when inserted in the subject's ear, will conform to the shape thereof. The sound transmitting passageways are drilled rather than formed-in-place. Much labor and at least one visit to check the fit can be eliminated if such custom-molded devices are formed-in-place, that is to say, cast in the ear and hardened.